Trick en­gine changes its ca­pac­ity

BMW X3 ri­val wades into bat­tle with re­mark­able en­gine tech and eye-catch­ing looks


Now here’s an odd­ity: the cu­bic ca­pac­ity of the Infiniti QX50’S en­gine shifts be­tween 1970cc and 1997cc. It’s the first masspro­duced car in the world to fea­ture this strange char­ac­ter­is­tic, and that’s be­cause it has the world’s first mass-pro­duc­tion vari­able com­pres­sion ra­tio en­gine.

Be­sides be­ing of slightly fluid in­ter­nal size, the com­pres­sion ra­tio of the QX50’S all-new four cylin­der en­gine varies be­tween 8.1:0 and 14.1:0. Al­ter­ing the com­pres­sion ra­tio of an en­gine has long been the holy grail of in­ter­nal com­bus­tion en­gi­neers. The com­pres­sion ra­tio is the mul­ti­ple of units of at­mo­spheric pres­sure pumped by the pis­tons, and the new-found abil­ity to al­ter this ra­tio pro­vides an­other means of fine-tun­ing mix­ture for an op­ti­mal, ef­fi­ciency-en­hanc­ing fuel burn. In fact, Infiniti claims that its ap­prox­i­mately 2.0-litre Vari­able Com­pres­sion-turbo en­gine (VC-T) com­bines the power of the V6 that it re­places and the fuel con­sump­tion of a sim­i­larly sized V6 diesel.

It’s cer­tainly a pokey en­gine. Peak power is 264bhp, and max­i­mum torque a stout 280lb ft that’s con­sis­tently avail­able be­tween 1600rpm and 4800rpm. In the QX50’S case, it has a not in­sub­stan­tial 1753kg to pro­pel, but it feels brisk on the road. And as the revs rise, in­creas­ingly un­usual, too.

The VC-T mo­tor is smooth, al­though this ad­van­tage tends to be over­shad­owed by its slightly gritty sound at low revs. This swells to a light whine un­til you hit 4000rpm, when a keen throt­tle pro­duces a noise like an old-school twin-cam four pound­ing out its best ef­fort. It sounds slightly ar­ti­fi­cial, which it is, in fact – noise-gen­er­at­ing and can­celling tech­nolo­gies adding to the au­ral mix. The rorty sounds tail off as 6000rpm ap­proaches or im­me­di­ately you drop the throt­tle, the fall in crank speed ac­cen­tu­ated by the fact that the en­gine is hooked to a con­tin­u­ously vari­able trans­mis­sion. Th­ese in­ge­nious, steel belt-driven gear­boxes are ef­fi­cient – hence the rea­son for this trans­mis­sion choice, says Infiniti – but, as any Toy­ota Prius owner knows, you end up with the sound­track of an in­de­ci­sive power tool user.

This is par­tic­u­larly true on a twisty road, when the rise and fall of the throt­tle as you en­ter and exit each bend is matched by the rise and fall of the two-piece en­gine and trans­mis­sion en­sem­ble. You can lessen that ef­fect by us­ing the QX50’S pad­dle shifts, which in­tro­duce ar­ti­fi­cial gears and bet­ter al­low you to ex­ploit the grippy chas­sis. The Infiniti slices bends pretty ef­fec­tively, its on-de­mand all-wheel drive adding sta­bil­ity as well as quelling mo­men­tary torque-steer squirms, but this is no sports SUV de­spite the some­times racy sounds.

The cabin, in any case, sug­gests oth­er­wise, what with the leather and maple­wood decor pro­vided by the range-top­ping Es­sen­tial ver­sion. Pleas­ingly soft quilted hide, a finely trimmed fas­cia and that classy open-pore wood add to the up­mar­ket am­bi­ence, as does a suede-ef­fect head­lin­ing. Much of the in­te­rior looks taste­fully ex­pen­sive, but closer ex­am­i­na­tion re­veals slightly cheap­look­ing, old-school in­stru­ments, a low-rent steer­ing wheel boss and a sat-nav dis­play that could use more clar­ity-en­hanc­ing def­i­ni­tion. And the strange, suede-like in­serts to the dash­board and doors re­sem­ble an anti-rat­tle ma­te­rial.

It’s an im­pres­sively prac­ti­cal in­te­rior, though. One ben­e­fit of down­siz­ing from a V6 to a trans­verse four-cylin­der of tight-packed an­cil­lar­ies is the re­lease of more cabin space. The QX50’S rear room is gen­er­ous, even if you can’t snug­gle your feet be­neath the front seats. The rear seats slide to in­crease the vol­ume of an al­ready gen­er­ous boot, which is the re­sult of ef­forts to re­duce the bulk of the multi-link rear sus­pen­sion.

Plenty of thought has been in­vested in this car, from pow­er­train to pack­ag­ing to style, a fur­ther ben­e­fit of the VC-T tech­nol­ogy be­ing best-in­class fuel economy in the US, which bodes well for Europe. A shame, then, that the QX50 lacks the ul­ti­mate pol­ish of BMW’S X3, for in­stance, its re­fine­ment, in­tru­sive trans­mis­sion and patchy low-speed ride a too ob­vi­ous con­trast to its po­tency and roomily dis­tinc­tive in­te­rior.

Crisp styling out­side is matched by a dis­tinc­tive-look­ing cabin that ex­udes an up­mar­ket am­bi­ence

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